(_ UnitedStates

Departmentof

Agriculture " In Pursuit of a Better Seed Trap

" ForestService

NorthCentral " Adam Wiese John Zasada, and Terry Strong Research . t

Station

•- ResearchNote

NC-373..

ABS'I'RACr.--Seed and litter traps are tools The choice of trap should be based on such

used by foresters and ecologists. We describe considerations as type of seed dispersal unit,

two different types of a durable trap con- timing of dispersal, and expected density of

structed from plastic plumbing pipe, which are seedfall. For example, Walker et al. (19861

J easily assembled/disassembled for efficient used traps containing water to estimate seed

transportation and storage, rain of Salicaceae seeds, and they used more

• standard wood frame traps for Picea and Alnus

KEYWORDS: seed production, litter produc- seeds. Cameron and Foreman (1997) reported

t.ion, forest regeneration, that traps With larger collection areas (up to 4

m 2)may be necessary to estimate seed density

when seed crops are small, while small traps .

Seed and litter traps have been used for (0.25 m2) may be adequate during years of

decades byforesters and forest ecologists to high-density seed rain. Species differ in the

monitor various aspects of production and potential magnitude of seed production.

dispersal of seeds and litter. The method of Birch, for example, consistently has greater

Construction and materials used, as well as seed production than white spruce. Thus,

the shape and size of the traps, vary depend- small seed traps (e.g., 0.25 m2) may be approing onthe specific needs of the project and the priate for birch, while larger traps (1 m2) may

resources available to make or buy the traps; be necessary to obtain reliable estimates for

often, any convenient type of container that white spruce.

can catch and retain seeds is used. The most

Most trap designs have strengths and weak- traditional design is a wooden frame with a

screen bottom, with (seed trap) or without nesses. Wood frame traps if not made from

(litter trap) a hardware cloth top, and with a treated wood eventually deteriorate. Dependsurface area of 2.6 to 10.6 ft2 (Leadum eta/. ing on their size, they may be diiTicult to store

1997) 1. However, many other types of traps and may be unwieldy and difficult to carry into

have been used, e.g., funnel-shaped traps relatively remote sites. Traps with cloth,

elevated 3 to 4 ft above the soft surface or top plastic, or screen bags (Hughes et aL 1987)

•set at ground level (Christisen and Kearby attached to metal frames may be unstable with

1984; Sarvas 1962, 1968; Zasada and Gregory snow loads, and the bags are often the target

1972), traps with cloth or screen bags at- of bears, squirrels, and other animals. Howtached to some type of metal frame (Hughes et ever, these traps are very portable, inexpenaL 1987), traps containing water or a commer- sive, and more readily stored than wood frame

ciaUy available soil mixture that catches seeds traps. Traps that use water or a soil mix are

and allows them to germinate in place (Walker difficult to maintain because water needs to be

et a/. 1986, Zasada and Densmore 1979), added to them periodically for proper functionplastic buckets (Jones et al. 19941. and traps ing.

• With a sticky surface (like fly paper) to which

seeds adhere.

Adam Wiese is a Forestry Technician, John

Zasada is a Project Leader, and Terry Strong _Metric equivalents of English units used in

•is a Research Forester with the North Central this report: I foot = 30.48 centimeters or

Research Station in Rhinelander, Wisconsin. 0.3048 meter; 1 square foot = 0.0929 square

meter; 1 inch - 2.54 centimeters.
In search of a trap that might be more durable FLAT TRAP

for both summer and winter use, easily trans-

" ported, and efficiently stored when not in use, The materials and equipment needed to conwe have designed-a trap constructed of stan- struct a trap (fig. 1A) with a sampling surface

dard plasticpipe used in home plumbing area of 7.4 ft2 (33 in. x 33 in.) are as follows:

(PVC). Although this trap may not be perfect

for all applications, it provides another design Flat Trap Materials List

to consider. In the following, we describe how

to build a fiat trap similar to the traditional 1. 30 ft of PVC pipe

wood frame trap as well as a deeper basket 2. Eight 90 ° elbows (PVC)

trap that is similar to the funnel-type trap. 3. Four 3/8 in. dowel rods

PVC, rigid by nature, has many accessories 4. PVC cleaner

(i.e., T-joints, various angle joints) that allow 5. PVC cement

for flexible design options. The .traps we 6. 12 ft of weather stripping

describe are but two examples of options made 7. Nylon screen (comes in 3 ft widths)

available by the use of PVC. 8. Hardware cloth (1/2 in. openings)

• ' !

I

Figure 1._(A) Lower half of flat trap with screen bottom and top half of trap with hardware cloth

unassembled. Longer pieces are trap frame; note slots into which dowels or hardware cloth fit.

• Shorter pieces are legs (see 1D). Note darker area just inside assembled frame--this is the seam

that forms the sleeve for a dowel. (B) Arrow nearest center of photo shows gray weather strip2 ping. Black cable tie holds trap together at other arrow. (C) Top view of assembled trap; inset

shows hardware cloth top and screen bottom. (D) Ftdly assembled trap with legs.
9. Propane torch The procedure we used in constructing the fiat

10. Copper tubing 1 ft x 1/2 in. diameter traps can be broken down into the following

11. Cable ties steps.

12. Drill and drill bits of assorted sizes

13. Table saw Step l.--Cut the PVC pipe into eight 33-in.

14. Miter saw sections (fig. IA). This length will make the

outside seed trap dimensions 36 in. x 36 in.

We chose these trap dimensions because both when the 90" elbows are added to these pieces.

the nylon screen and hardware cloth were We used a compound miter saw in this step.

available only in 36-in. widths. Traps with a

larger surface area could be easily con- Step 2.--Cut pipe sections so that a slot is

structed, but both the screen and hardware formed through one of the two walls of the

cloth would have to be spliced to make larger PVC (fig. 1A, 2C). To safely cut these sections,

pieces, clamp a block of wood to the table saw so that

the saw blade is centered between the fence

Figure 2.--(A) Unassembled frame for basket trap. (B) Screen basket showing bonded seams. The

wooden dowels are shown (1 and arrow) positioned in sleeves. (C) Comer of frame showing Tjunction, 90" elbow, and slot (1 and arrow) through which the dowels are inserted to hold the

basket securely in place. (D) Top view offully assembled trap.

3
and the block of wood to guide the sections insert the screen from the other end of the

through the saw. PVC (fig. IA, 1C).

Step 3.---Cut the 90 ° elbows as in step two. Step 6.---Stick weather stripping to the top of

This cut is a little more difficult to make (fig. the PVC section that holds the nylon screen.

IA, 2C). The 90" angles should be placed on Then, place the top and bottom of the trap

edge with the point of the angle facing upward, together, sandwiching the weather stripping

Onceyou've made these cuts, put the PVC (fig. 1B).

together so that the slots are all in line (do not

glue together). Step 7.---Finish the trap by drilling holes

through both halves, allowing room for cable

Step 4.__ iron or other material that can be ties to be inserted and cinched together. Cable

heated to bond/melt the nylon screen together ties may be added to the section of the seed

is needed for this step. We use d a piece of trap that holds the hardware cloth to the PVC

copper tUbing 1/2 in. in diameter. The end of if so desired for extra support (fig. 1B).

the tubing was placed in a vice and flattened,

creating an ironing surface 1 in. wide. The Step 8._If the trap needs to be off the

flattened surfacewas then bent to about a 30" ground, make legs for it by using a hole saw

angle. The flattened end was heated with a ° that matches the diameter of your PVC. Simpropane torch to a temperature that melted ply take the PVC and drill through both wails;

two sections of nylon screen together, creating this will create a concave or (U) shape in the

a solid bonded screen. PVC on one end and act as a cradle for the 3-ft

x 3-ft frame. Now you can make a straight cut

The dowel rods are to hold the nylon screen in on the other end of the PVC to the desired leg "

the slotted PVC (fig. 1A, 2B) and should be 33 length. This will hold the fiat trap in place

•in. long. Once you've cut the rods, roll the once the legs are driven into the ground to the

'nylon screen Out on a good size table so that desired trap height (fig. 1D).

there is plenty of room to work. Center one of

the dowel rods on the screen approximately 1 BASKET TRAP (LITTER)

in. from the edge Ofthe screen. Roll or fold the

screen over so that there is room for the dowel The basket trap (fig. 2D) described here is 18

to slide easily into the sleeve and about 1-in. in. in length, width, and height. For traps

additional screen (fig. 2B). At this time, the with these dimensions, the following materials

propane torch is needed to heat the iron. are needed:

Once the iron is heated the screen can be

melted together forming a small sleeve that will Basket Trap Materials List

hold the dowel rod (fig. 2B). Slide the dowel

into the sleeve, and slide the screen and dowel 1. 20 ft of 3/4-in. PVC

into one of the slots that was cut into the PVC. 2. Eight 90" elbows

•Use this same procedure for the opposite end 3. Sixteen 3/4-in. "Fs

• of the screen. Now that two sleeves have been 4. PVC cement

formed, each holding a dowel rod, the same 5. PVC cleaner

must be done on the remaining two sides (fig. 6. Propane torch

2B). 7. Copper tubing to make iron

8. Nylon screen

Step 5._The hardware cloth for the top of the 9. Dowel rods (3/8 in. in diameter)

trap must be cut so that a 90" bend can be 10. Table saw

made on two sides only. Because the hard- 11. Miter saw

ware cloth is rigid, this bend is all that is

needed to hold it firmly inside the slots of the Step l.--Cut sixteen 12-3/4-in. pieces of 3/4-

PVC. At this time, the PVC cement and in. PVC.

cleaner will be used to secure one of the 90 °

elbows to one section of the PVC that mea- Step 2.---Cut sixteen 1-1/8-in. pieces from the

sures 33 in. Be sure to secure only one 90" remaining 3/4-in. stock. These pieces will be

elbow to one section of PVC so that you can used to connect the 3/4-in. T's to the 90 °
angles. Only half of these 1-1/8-in. pieces will

treed to have slots cut through one of the two The main reason we designed both the fiat

" wails of the PVC (fig. 2C). The remaining trap and the basket trap in this fashion was to

1-1/8-in. pieces will be used on the bottom of create a sturdy, but light and collapsible

the litter trap. Before cutting the 1-1/8-in. structure that can be easily transported and

pieces to size, cut a section of the PVC from stored. The traps are constructed from matewhich the smaller pieces'wiU be cut later; it is rials that will hold up for many years when

easier and safer to cut the slots in the longer used in the field. These materials are readily

piece, available but have not been commonly used

for construction of seed traps. The use of

Step 3.---With the table saw, cut the slots in PVC, in conjunction with a large assortment of

four of the 12-3/4-1n. pieces (fig. 2C), the 90 ° angles, diameters, and differing lengths,

elbows, and the "Us (fig 2C). Cut the slots in- makes these trap designs adaptable to many

0nlyone-half of the 90 ° elbows and the "Fs; the scientific needs and configurations.

remaining pieces will be used on the bottom of

the litter trap. When cutting the 90 ° elbows, LITERATURE CITED

_ remember to cut the groove with the outside of

the 90 ° angle facing upward (the ope ,n_ngs Cameron, D.A., Forman, F.I. 1994. Seed

facing down). When cutting the slots in the trapping to monitor operational aerial

T's, lay the T on its side and cut across the seeding. Tech. Note 43. Natural Resources

straight portionof it (fig. 2C). After making all Canada, Canadian Forest Service. 4 p.

cuts, assemble the trap to make sure the slots

are.all aligned (fig. 2C). Christisen, D.M.; Kearby, W.H. 1984. Mast -

measurement and production in MisSteP 4.---After assembling the frame work, souri (with special reference to acorns).

• remove one of the sides. Make sure that only Terrestrial Ser. 13. Jefferson City, MO:

one of the upper 90 ° elbows stays with each of Missouri Department of Conservation.

the four sides; this will allow for bag installa- 34 p.

tion. Now, carefully clean and cement together

one piece at a time, making sure that all of the Hughes, J.W.; Faney, T.J.; Browne, B. 1987. A

slots are aligned (fig. 2C). Do this for the better seed and litter trap. Canadian

remaining three sides of your trap. DO NOT Journal of Forest Research. 17" 1023-

Cement all four sides together! 1024.

Step 5.--Bond the nylon bag together in the Jones, R.H.; Sharitz, R.R.; Dixon, P.M.; Segal,

same manner as in the flat trap. Cut one D.S.; Schneider, R.L. 1994. Woody plant

piece of screen, 76 in. x 14 in. This section of regeneration in floodplain forest. Ecoscreen will make up all four sides of the bag logical Monograph. 64: 345-367.

•including the sleeves for the dowel rods. Once

the sleeves have been made and are holding Leadum, C.L.; Gilles, S.L.; Yearsley, H.K.; Sit,

the dowel rods (fig. 2B), it is a good idea to V.; Spitflehouse, D.L.; Burton, P.J. 1997.

place the screen, sleeve, and dowels into the Field studies of seed biology. Land

slots to check the fit before melting the screen Manage. Handbk.40. British Columbia

together. After checking the fit, melt the ends Ministry of Forestry, Research Branch.

together to form a square. 196 p.

Step 6.--When making the bottom section of Sarvas, R. 1962. Investigation on the flowerthe basket, be sure to leave enough screen so ing and seed crop of Pinus silvestris

that there will be at least a 2-in. overlap for a Comm. Inst. Forest Fenn. 53.4

seam. The bottom section of screen should be

approximately 22 in. x 22 in. Once this sec- Sarvas, R. 1968. Investigations on the

tion of screen has been secured to the bottom flowering and seed crop of Picea abies.

of the basket, the litter trap assembly can be Communicationes Instituti Forestalls

completed (fig. 2D). Fenninae. 67.5. 84 p.

.

5
Walker, L.; Zasada, J.; Chaprin, F.S. 1986.

The role of life history processes in

primary succession on an Alaskan

floodplain, Ecology. 67" 1243-1253.

Zasada, J.; Densmore, R. 1979. A trap to

measure Populus and Salix seedfall.

Canadian Field Naturalist. 93: 77-79.

Zasada, J.; Gregory, R. 1972. Paper birch

seed production in the Tanana Valley,

Alaska. Res. Note PNW-177. Portland, OR:

U.S., Department of Agriculture, Forest

Service, Pacific Northwest Research Station. 7 p.

J

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